Hydrostatic delay action fuse

ABSTRACT

A hydrostatically operated fuse having a pressure sensitive movable piston fixed to a rack and pinion gear arrangement. The movement of the piston corresponding to the working depth of the fuse is transmitted by the gears to a rotating cam device which may be preset to actuate a spring driven runaway escapement mechanism at any one of a number of selected depths represented by the size of the arc through which the cam must turn. The escapement mechanism controls a firing pin release mechanism which is actuated a predetermined time interval subsequent to the escapement actuation. A soluble salt washer device prevents the pressure sensitive piston from being exposed to the ambient pressure for a predetermined time.

United States Patent [1 Brennan HYDROSTATIC DELAY ACTION FUSE [75] Inventor: John A. Brennan, l-lyattsville, Md.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

22 Filed: July 29,1970

21 Appl. No.: 64,914

[4 1 May 20, 1975 Primary Examiner-Robert F. Stahl Attorney, Agent, or Firm-R. S. Sciascia; J. A. Cooke 5 7 ABSTRACT A hydrostatically operated fuse having a pressure sensitive movable piston fixed to a rack and pinion gear arrangement. The movement of the piston corresponding to the working depth of the fuse is transmitted by the gears to a rotating cam device which may be preset to actuate a spring driven runaway escapement mechanism at any one of a number of selected depths represented by the size of the are through which the cam must turn. The escapement mechanism controls a firing pin release mechanism which is actuated a predetermined time interval subsequent to the escapement actuation. A soluble salt washer device prevents the pressure sensitive piston from being exposed to the ambient pressure for a predetermined time.

4 Claims, 7 Drawing Figures PATENTED MAY 2 01975 SHEET 10F 3 NNN 1 HYDROSTATIC DELAY ACTION FUSE BACKGROUND OF THE INVENTION This invention relates generally to a delay action ordnance fuse and more particularly to an underwater fuse mechanism for setting off a charge of explosive at a predetermined future time after a predetermined depth is reached.

In anti-submarine warfare, explosive charges attached by swimmers to the hulls of moored enemy vessels, such as submarines, have proved to be extremely effective devices. In the past, the majority of these devices have been equipped with conventional hydrostatic pressure responsive type fuses adapted to be actuated when the submarine to which the device has been affixed descends to a predetermined depth. Problems have arisen, however, when a plurality of explosive devices of this type have been fastened to the hull of the submarine in longitudinal spaced relation. More specifically, as the submarine descended deeper below the surface in an angular fashion, the explosive device located towards the bow of the submarine would be exposed to the before mentioned predetermined depth prior to the devices located further aft thereof. The consequence of this is oftentimes after the first device sees the predetermined depth and is actuated, the submarine was not damaged sufficiently to prevent an immediate cessation of the dive and a subsequent surfacing of the vessel. As a result, the remaining explosive devices would remain unactivated.

It would appear to be desirable, therefore, to provide an explosive device with a fuse which, after the predetermined depth is attained, delays the initiation of the charge for a fixed amount of time. The provision of such a time delay would allow the entire submarine and the plurality of explosive devices fixed thereto to exceed the predetermined depth level and thereby assures the efficacious explosive detonation of all the devices.

SUMMARY OF THE INVENTION Accordingly, one object of this invention is to provide a new and improved fuse apparatus for underwater weapons.

Another object of the invention is the provision of an improved hydrostatic pressure responsive fuse.

Still another object of the instant invention is to provide a pressure responsive fuse having a variable depth setting capability.

A further object of the present invention is to provide a new and improved pressure responsive fuse which will not function for a predetermined time interval after the fuse has been exposed to a predetermined hydrostatic pressure.

Briefly, in accordance with one embodiment of this invention, these and other objects are attained by providing a fuse with a pressure sensing mechanism adapted to actuate a release and depth setting mechanism at any one ofa number of possible depths at which time a delay timer mechanism is initiated by the release mechanism. After a predetermined amount of time elapses, the delay timer actuates a firing pin release mechanism which permits a firing pin to be moved with great velocity into an explosive charge.

BRIEF DESCRIPTION OF THE DRAWING A more complete appreciation of the invention and many of the attendant advantages thereof will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a side view, in full section, of the fuse according to the present invention;

FIG. 2 is a front view of the fuse;

FIG. 3 is a sectional view on the line 3-3 of FIG. 1;

FIG. 4 is a sectional view on the line 4-4 of FIG. 1;

FIG. 5 is a side view of the depth setting mechanism in partial section;

FIG. 6 is a perspective view of the dial and release cam of the present invention; and

FIG. 7 is a cross-sectional view of the firing pin taken along line 77 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings wherein like reference characters designate identical or corresponding parts throughout the several views, and more particularly to FIG. 1 thereof, the hydrostatic delay action fuse of the present invention is shown as including a fuse housing 10 formed of a generally cylindrical body portion 12 surrounded by a cover 14 and a salt washer housing generally denoted at 16 threadedly connected to one end of fuse housing 10 by threads 18. Body portion 12 houses a hydrostatic pressure sensing mechanism 20 as will be described in more detail hereinafter which is prevented from being exposed to ambient hydrostatic pressure by the apparatus contained in salt washer housing 16.

The salt washer housing 16 includes a transparent cylindrical housing cover 22 and a circular cap 24 attached thereto having a flanged rim 26. A set screw 28 cooperates with the rim 26 and sits within an annular groove 29 in housing cover 22 thereby permitting relative angular movement while prohibiting relative longitudinal movement between cap 24 and housing cover 22 for reasons to be more fully discussed hereinafter. Cover 22 includes three axial internal bores, the smallest of which, bore 30, opens into the end of the housing immediately adjacent cap 24. A counterbore 32 of larger size than bore cooperates therewith, thereby forming an annular shoulder 34 and a second counterbore 35 communicates with counterbore 32 at one end thereof and opens into the end of housing 22 furtherest from circular cap 24. A soluble washer disc 36, which may be made of any one ofa number of soluble materials, such for example, as a mixture of 80 percent bicarbonate and 20 percent sodium chloride compressed at 8,000 psi, is fixedly positioned within salt washer housing 16 by the cooperation of a fixed piston 38 and an opposed movable piston 40. Piston 40 includes a flat circular plate 42 which is positioned against a side 43 of the soluble washer 36 and is connected to an elongate shaft 44 having an annular groove 46 containing an O-ring seal 47 therein. The shaft 44 is slideably positioned in a bore 48 contained within a transverse wall 50 of a cylindrical piston housing 52 having a partially externally threaded portion 54 fixedly connectable to the threads 18 of body portion 12. Cylindrical wall 56 of piston housing 52 defines an internal piston bore 58 in which the piston plate 42 may slide. A compression spring 59 biases plate 42 against side 43 of the soluble washer 36. The soluble washer 36 is retained throughout a substantial portion of its circumference by the inner surface of bore 58. The cylindrical wall 56 includes a relatively shortened portion as shown at 60 forming a slot 61 in piston housing 52 and as a consequence, the circumference of the soluble washer 36 adjacent to the formed slot 61 is not physically constrained in any way.

Fixed piston 38 includes a circular flat plate 62 and a cylindrical shaft 64 connected thereto having an annular groove 66 formed therein containing a seal 67. A second cylindrical shaft 68 of reduced diameter is formed integrally with the first shaft and positioned at the end thereof. Plate 62 is fixed in abutting relati'onship against side 70 of soluble washer 36 by conventional means such as screw 72 which is threadedly fastened into wall 56 of piston housing 52.

Piston housing 52 includes a circumferentially extending enlarged portion 74 substantially adjacent to threaded portion 54 which has a circumferential groove formed therein for retaining a seal member 76. The salt washer housing cover 22 is fitted over the enlarged portion 74 of piston housing 52 with the shaft 68 of fixed piston 38 extending through a rectangular central opening 78 in the circular cap 24. The entire salt washer housing 16 is biased in a direction opposite from body portion 12 by means ofa compression spring 80 positioned about shaft 64 in a compressed state and whose ends abut against shoulder 34 and piston plate 62. A rectangular head 82 fixed to shaft 68 retains the salt washer housing 16 in place against the force of spring 80 as best seen in FIG. 2. Cap 24 further hasv formed therein an arcuate opening 84 which upon rotation of the cap 24 to an appropriate position will cooperate with a bore 86 formed in housing cover 22 for reasons to be discussed in greater detail hereinafter. Housing cover 22 has an annular groove 88 formed in its end adjacent the inner surface of cap 24 and surrounding the bore 86 in which an O-ring seal member 90 is positioned. The necessity for the sealed bore 86 and cooperating opening 84 will become more apparent when the operation of the invention is more fully described hereinafter.

Positioned immediately behind the transverse wall 50 of piston housing 52 in body portion 12 is the pressure sensing mechanism 20. A longitudinally directed bore 92 is formed within body portion 12 and cooperates with a cylindrical cavity 94 formed in a forward position of body 12. Movably positioned within cavity 94 is a piston 96 integral with a rack 98 which slides within bore 92. The piston and rack assembly is biased towards the salt washer housing 16 by a spring 100 whose ends bear against the rearward wall of cavity 94 and a shoulder portion on piston 96. A diaphragm 102 is fastened to the front edge of body portion 12 by a circular retaining member 103 which substantially encloses the piston 96 within the diaphragm as at 104. Retaining member 103, which may be fastened to body portion 12 by screws 105, includes a central substantially circular raised portion 106 which serves to restrain the piston 96 against the force of spring 100. Two diametrical slots 108 are formed at right angles to each other which effectively expose diaphragm 102 to the ambient environment present between transverse wall 50 and retaining member 103 to be discussed in greater detail hereinafter.

Intersecting bore 92 at right angles thereto is a transverse cylindrical cavity 110 opening into the outer surface of body portion 12. Contained within cavity is a pinion and spur gear assembly 112 having a shaft 114 whose ends 116 are rotatably mounted in a bore 118 and cylindrical bearing member 120 affixed within cavity 110.

Axially offset from cavity 110 and cooperating therewith is a cylindrical bore 122 which opens into an axially aligned counterbore 124 of greater diameter and which defines an annular shoulder 126 in cooperation with a second counterbore 128. Rotatably positioned within bore 122 and extending into counterbore 124 is a shaft 130 having a gear 132 connected at one end thereof which cooperates with the pinion and spur gear assembly 112. Fixed to the lower portion of shaft 130 and adapted to rotate with the shaft is a female sprocket assembly 134 including a bearing 136 and a disc-shaped female sprocket 138. A male sprocket assembly slideably mounted on the upper portion of shaft 130 cooperates with the female sprocket 138 in any one of a number of selected positions. The male sprocket assembly 140 includes a dial and release cam 142 to be described presently and a male sprocket 144 fixed thereto. The male sprocket 144 is of a substantially cylindrical shape having on its lower rim an upwardly formed tooth 146. The female sprocket 138 includes a series of circumferentially spaced, tooth receiving slots, such for example, as 148. The male sprocket assembly is biased in an uppermost position by spring which cooperates with dial and release cam 142 to allow the tooth of male sprocket 144 to mesh with the slots of the female sprocket 138 in a positive fashion. It should be apparent, therefore, that the male sprocket 144 can be selectively engaged with the female sprocket 138 in any one of a number of angular positions and when so engaged, will move as an integral portion thereof. To vary the position of the male sprocket assembly 140 with respect to the female sprocket assembly 134, it is only necessary to depress the male assembly 140 against spring 150 thereby disengaging the teeth from their slots while turning the male sprocket assembly to a new position. The reasons for so doing will be made apparent hereinafter.

The dial and release cam 142 is positioned on shaft 130 above the male sprocket 144 and is of a disc-shape having a substantially circular cross-section with a centrally disposed cylindrical bore 151. A centrally disposed slotted protrusion 145 is also provided for reasons to become apparent later. The functional contour of cam 142 is formed by slicing a portion of the disc along an imaginary chord leaving only a lower onequarter of the material 152 remaining forming a step 153 as best seen in FIG. 6. The cam 142 is normally fixed to the male sprocket 144 by means of a set screw 154 which is positioned within an arcuate groove 155 in the cam which overlies a threaded bore 157 in the male sprocket 144. It should be evident, therefore, the dial and release cam 142 may be fixed to the male sprocket 144 in any one of a number of positions by merely loosening screw 154, rotating cam 142 and retightening the screw. This feature is utilized for precise calibration techniques which will be more fully explained in the description of the operation of the invention hereinafter. Cam bore 151 extends above the end of shaft 130 so as to permit the male sprocket 144 to be depressed as discussed hereinbefore.

Referring now to FIG. 4, it will be seen that substantially adjacent to and rearward of male and female sprocket assemblies 140 and 134 is a conventional spring driven runaway escapement mechanism 156 whose details will not be described since of a conventional nature. Directly geared to the escapement is a rotatably mounted shaft 158 having a key 160 comprising a rod integrally mounted perpendicular to the axis thereof. When escapement 156 is in its energized state, that is, when the mainspring has been wound, the mechanism is normally prevented from operating by an elongate release arm 162 which includes a downward facing projection 164 at the rearward extremity thereof which contacts escapement gear 166 thereby preventing its rotation. Release arm 162 is positioned alongside dial and release cam 142 transverse to the longitudinal axis thereof and further includes a follower 168 attached to the release arm midway along the length thereof which is normally in contact with the circular surface 170 of cam 142. A pivot 172 is provided at the forward end of release arm 162 and the arm is biased in a clockwise direction as seen in FIG. 4 by virtue of a compression spring 174 housed in a bore 176. A cylindrical member 178 is fastened to the end of the spring and cooperates with a threaded member 180 positioned at the end of arm 162 thereby effecting the biasing force.

When the follower 168 of release arm 162 is in contact with the circular surface 170 of the dial and release cam 142, the projection 164 is forced into contact with the escapement gear 166 and thereby prevents the operation of the escapement mechanism 156. However, it should be apparent that if cam 142 rotates in the direction of arrow 182, to be more fully described hereinbelow, the step 153 in the releasecam will align with the follower 168 on the release arm 162. As a result of the biasing discussed hereinbefore, the release arm pivots in a clockwise direction thereby unlocking the spring driven escapement 156.

Referring again to FIG. 1, a firing pin release mechanism, generally denoted as 182, is shown as positioned within a firing pin release housing 184 which is fixed to an end of cylindrical cover 14 by conventional means, such for example, as screws 186. The release housing 184 has formed therein an internal cylindrical bore 188 which cooperates with an axially aligned counterbore 189 forming a shoulder 190. A circular wall 192 having a central opening 194 is fixed in abutting relationship to shoulder 190. Immediately adjacent to wall 192 a conventional ball bearing 196 is positioned within counterbore 189. Fitted rotatably within the inner race of bearing 196 is a cylindrical firing pin retaining drum 198 having a central cylindrical bore 200 which extends the length thereof and an inwardly disposed lip 202 at one end which defines a rectangularly shaped opening 204. The bore 200 in the retaining drum 198 is adapted to fixedly receive key 160 of shaft 158 by providing matching openings (not shown) for the key.

Slidably positioned within and extending the length of bore 188 and counterbore 189 is a firing pin 206 which is provided with transversely extending rectangular locking arms 208 at one end and an annular shoulder 210 in substantial proximity to the other end thereof. A compression spring 212 is positioned about the firing pin 210 which abuts the wall 192 and annular shoulder 210 of the firing pin. The spring 212 is held in its compressed position by positioning firing pin 206 such that the locking arms 208 are within the retaining drum 198. it is obvious that as long as the opening 204 in the retaining drum 198 is not aligned withthe locking arms 208, the firing pin 206 will beheld in position despite the biasing force of spring 212.

In operation, a swimmer will attach an explosive mechanism incorporating the fuse of the present invention to the hull of an enemy vessel, such as a submarine, while moored. Initially, a primary locking device 214 including an elongate rod 216 positioned in a bore 218 formed mutually in the housing cover 22 and circular cap 24 to prevent relative angular movement therebetween is removed by the swimmer. The cover 22 and cap 24 are thereafter removed by rotating the cap in either a clockwise or counterclockwise direction. As this is done the arcuate opening 84 (FIG. 2) in the cap 24 will align itself with bore 86 in cover 22 thereby allowing water to enter within and equalize the hydrostatic pressure on either side of the cap. When head 82 is aligned with opening 78, the compression spring 80 pops the cover and cap off the piston housing 52 thereby exposing the soluble washer 36 to the external atmosphere. The time required to dissolve the salt washer 36 varies depending on water temperature and current, however, it usually should require a minimum of 30 minutes to dissolve in water at a temperature of F with a l knot current. As the washer 36 dissolves, the movable piston 40 advances towards the piston plate 62 of fixed piston 38 propelled by the force of spring 59. After the soluble washer 36 has dissolved a predetermined amount, the portion of piston plate 42 of the movable piston 40 which had been cooperating with the shortened wall portion 60 of piston housing 52 moves to a position opposite slot 61 thereby allowing the free entry of water into piston bore 58. By the time soluble washer 36 has almost completely dissolved, the seal formed by the O-ring 47 cooperating within bore 48 is broken by virtue of the O-ring having been removed from the bore. The ambient pressure will then be allowed to act on the diaphragm 102 of pressure sensing mechanism 20.

As the ambient pressure acts on the diaphragm 102 and increases due to increasing depth of the submarine, the piston 96 and rack 98 affixed thereto are moved in bores 92 and 94. The compression spring l00'opposes the force on the piston 96 transmitted by the diaphragm 102 and thereby controls the amount of piston movement for each incrementof pressure increase. The linear piston movement is transmitted to the piston and spur gear assembly 1 12 by rack 98 where it is transformed to rotary motion. The rotation of pinion and spur gear assembly 112 is then transmitted to the male and female sprocket assemblies and 134 through gear 132.

It is to be noted that the escapement mechanism 156 has been, during the entire sequence described above, in a locked position and maintained therein by the locking effect of projection 164 of release arm 162 on escapement gear 166. As discussed hereinbefore, as long as release arm follower 168 rides on the circular surface portion of dial and release cam 142, the escapement will remain in a locked position.

The female sprocket 138 is driven directly by gear 132 with the amount of rotation thereof determined by the size of the pressure increased as reflected by the movement of the pressure sensing mechanism 20. As described hereinbefore, the female sprocket 138 is slotted, as at 148, and each slot represents a depth setting. The male sprocket 144 is driven by the female sprocket when they are engaged and the dial and release cam 142 is locked into the male sprocket 144 and rotates therewith during operation. During rotation, follower 168 on the release arm 162 rides on the cam 142. When the follower 168 is aligned with the step 153 on the cam 142, the release arm 162 pivots under the force of spring 174 (FIG. 4) in a clockwise direction thereby freeing the escapement gear 166 of the locking effect of projection 164 thus allowing the escapement mechanism 156 to begin operationv The pressure at which release occurs is determined by the are, such for example, as A in FIG. 4, through which the release cam 142 must rotate in order to align the step 153 in the release cam with the follower 168. A change in depth setting is accomplished by increasing or decreasing the arc. This is accomplished by depressing the dial and release cam 142 thus disengaging the male and female sprockets and rotating the male sprocket 144 with the attached cam 142 independent of the female sprocket 138. The male sprocket assembly 140 is made accessible through a window 220 in the cover 14 by removing a seal screw 222. One need merely remove screw 222, insert a tool such, for example, as a screwdriver into the slot in protrusion 145, depress the male sprocket assembly 140, and set it to a new depth setting by suitably rotating and repositioning it with respect to female sprocket 138.

When the spring driven runaway escapement 156 is unlocked, the key 160 revolves at a predetermined rate and causes firing pin retaining drum 198 to rotate. The time required to rotate the firing pin locking drum 198 into the firing pin release position is controlled by the runaway escapement 156. Firing pin release is accomplished when the opening 204 in the retaining drum 198 is rotated into alignment with the locking arms 208 on the firing pin 206. It is to be noted that once the escapement release is accomplished should the submarine try to resurface, the release arm 162 has locked the male sprocket assembly 140 into position thereby preventing the relocking of the escapement.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A hydrostatic delay action fuse comprising:

a substantially cylindrical fuse housing;

means positioned within said housing for sensing changes in hydrostatic pressure;

means connected to an end of said housing for preventing said pressure sensing means from being exposed to ambient pressure for a predetermined time;

sprocket means, including a female sprocket geared to said pressure sensing means and a male sprocket adapted to mesh with said female sprocket in one of a plurality of positions and a compression spring normally biasing said male sprocket into meshed contact with said female sprocket, for converting changes in the ambient pressure into rotary motion;

a firing pin slideably held within said housing;

release means operably connected to said firing pin for controlling the operation thereof;

time delay means cooperatively associated with said firing pin release means for delayably actuating said release means a predetermined time interval after the initiation of the timing sequence of said time delay means; and

means connected to said sprocket means and rotatable therewith for initiating said time delay means in response to a predetermined rotation of said sprocket means.

2. A hydrostatic delay fuse as recited in claim 1 wherein said means for initiating said time delay means includes a cylindrical cam fixed to said male sprocket and a pivoted elongate release arm adapted to pivot from a first position wherein said time delay means is in its uninitiated state to a second position wherein said time delay means has been initiated, said arm and said cam having means cooperating to permit pivoting of said arm to its second position when said arm is in contact with one position of said cam only and to maintain said arm in said first position at all other times.

3. A hydrostatic delay action fuse according to claim 2 wherein said cam includes manually operable means integral therewith for varying the angular location of said one position of said cam with respect to said release arm by disengaging said male and female sprockets and revolving said male sprocket and the associated cam with respect to the female sprocket.

4. A hydrostatic delay action fuse according to claim 3 wherein said pressure exposure preventing means comprises a movable piston having a normally watertight seal at one end thereof and a water soluble salt washer adapted to be exposed to the ambient environment, said washer positioned in abutting relationship to said piston to prevent the movement thereof and consequent opening of said seal.

* l =l l 

1. A hydrostatic delay action fuse comprising: a substantially cylindrical fuse housing; means positioned within said housing for sensing changes in hydrostatic pressure; means connected to an end of said housing for preventing said pressure sensing means from being exposed to ambient pressure for a predetermined time; sprocket means, including a female sprocket geared to said pressure sensing means and a male sprocket adapted to mesh with said female sprocket in one of a plurality of positions and a compression spring normally biasing said male sprocket into meshed contact with said female sprocket, for converting changes in the ambient pressure into rotary motion; a firing pin slideably held within said housing; release means operably connected to said firing pin for controlling the operation thereof; time delay means cooperatively associated with said firing pin release means for delayably actuating said release means a predetermined time interval after the initiation of the timing sequence of said time delay means; and means connected to said sprocket means and rotatable therewith for initiating said time delay means in response to a predetermined rotation of said sprocket means.
 2. A hydrostatic delay fuse as recited in claim 1 wherein said means for initiating said time delay means includes a cylindrical cam fixed to said male sprocket and a pivoted elongate release arm adapted to pivot from a first position wherein said time delay means is in its uninitiated state to a second position wherein said time delay means has been initiated, said arm and said cam having means cooperating to permit pivoting of said arm to its second position when said arm is in contact with one position of said cam only and to maintain said arm in said first position at all other times.
 3. A hydrostatic delay action fuse according to claim 2 wherein said cam includes manually operable means integral therewith for varying the angular location of said one position of said cam with respect to said release arm by disengaging said male and female sprockets and revolving said male sprocket and the associated cam with respect to the female sprocket.
 4. A hydrostatic delay action fuse according to claim 3 wherein said pressure exposure preventing means comprises a movable piston having a normally water-tight seal at one end thereof and a water soluble salt washer adapted to be exposed to the ambient environment, said washer positioned in abutting relationship to said piston to prevent the movement thereof and consequent opening of said seal. 